It’s turnover time for key members of the Obama administration. And this morning the head of the EPA, Lisa Jackson, announced she’s leaving before the second term starts. Jackson departs a day after the U.S. economy stepped on the energy scale.

And, guess what, we’re skinnier. According to the Energy Information agency, Americans consumed 3 percent less energy than last year. And consumption is trending down.

Our cars guzzle less, in part because of Jackson’s agency.

“A big driver of that are EPA and Department of Transportation standards for fuel efficiency,” says former Obama White House energy counselor Jody Freeman, now teaching at Harvard Law. “And I think over time we’ll see that having a big impact in this story about driving down oil consumption down domestically.”

Also going down: carbon emissions. The U.S. is on track to meet its global commitment of reducing greenhouse gas emissions 17 percent by the year 2020.

Frank O’Donnell at Clean Air Watch credits new federal rules on tailpipes and power plants, under Jackson’s watch.

“She took a very bold step by declaring that climate change is in fact a threat to health and the environment,” O’Donnell says. “This was a legal finding that set in motion all attempts to deal with climate change.”

Of course regulations have benefits and costs. The impacted coal industry -- also contending with a cheap new rival, natural gas –- considered Jackson’s EPA public enemy number one.

And O’Donnell says the White House at times undercut Jackson’s efforts to regulate smog-inducing ozone emissions.

But the president’s second term could be different, and more aggressive on the regulatory front, with the reelection out of the way.

“Does the president seize the opportunity to press the green button,” says analyst Kevin Book of Clear View Energy, “and load the torpedo tubes at EPA and the other agencies with a spate of regulations? Or does he approach things more modestly?”

Book thinks the president’s state of the union speech next month will forecast how aggressive the EPA will be, in the post-Lisa Jackson era.